Method for forming slag-free thermite welds



J. H. DEPPELER un'mon FOR FORMING SLAG FREE THERMITE mamas Filed July16, 1925 INVENTOR HIS ATTORNEY Patented .May

un1'r|-:D STATES.

PATENT pip-mt, i

JOHN E. mums, or wnnmwim'n, NEWFJERSEY, nssrenon '10 Marni. & ram m'rconrona'riomor cnn'rnnnr, mzw-mnsnr, n-conronn'rron on NEW JERSEY.

Hermon ron ronnme sud-FREE rnnnm'rn warms.

Application flled July 16, 1925. Serial No. 48,916.

special fgrin of mold for carrying out the method.

Apparatus for, carrying out the method is illustrated in theaccompanying drawing,

in which:

The figure is a sectional elevation of a special mold.

It has been the generalpractice inwelding miscellaneouspieces, such aslocomotive frames, crank shafts and similar large castings, by thethermite. method, to'employ large molds using great quantities ofmolding material and having long runners or pouring gates leading theliquid thermite metal into the bottom of the mold space at. or near thebottomof the parts to be welded,

. the pouring gate usually being disposed at an angle to the vertical.Similarly, in rail welding by' the the'rmite method the pour ing gatewas lon and. oblique leading the liquid steel into the mold about thebase of the rail. I

Recently, however, it has been found desirable, for the purposerofreducing the cost of thermite Welding, and more completely eliminatingblow holes and similar defects from the welds, to greatly reduce thesize of the mold'and, therefore, the amount of molding sand used, and,as a consequence of this, the runners or pouring gates have necessarilybeen made shorter, less oblique or more nearly vertical. 1 .L kewlse',1n welding certain types of rails,it has been foundadvantageous todispose the pouring gate in the top of the mold adjacent the gauge facesof the rails and substantially in vertical alignment with the spacebetween the rail ends.

. It was not anticipated in'e'ither of these practices that theshortening of the'pouring gate and the disposition of the-same, eithervertically or would produce any harmful-or objectionable effects, but itwas frequently noticed that slag was found entrapped in the-welds produced with molds of'the types indicated; 4 .This objectionablephenomenonwas-especially noticeablefin rail welding involving the use of an insertbetween the rail ends adj acent the tread portions, as slag was almost'invariablytrapped under the in'sert.- Yar approximately vertically, I

beveling the under side of the insert to form a more or less abruptangle with the horizontal in the hope and expectation that this wouldpermit the slag to rise along the :inclined or beveled surfaces andpassoff through the riser, leavingnothing but cleanthermite steel underthe insert, without the intervening layerof slag, which preventedfusion-of the metallic parts wherever such slag was present. Neitherthis 'nor other cxpedients, which have been tried, obviated thedifliculity until the instant invention was developed and successfully'applied.

In thermite' welding,,a bottom pour crucible is suspended over the top"of thepoun lng gate of the mold and in this crucible the thermitereaction form's simultaneously a certain weight of liquid steel and acoin mensurate weight of molten sla the steel going to the bottom of thecruci le and the slag rising to the top. When the crucible,

is tapped by dislodging the plug or pin in the bottom opening thereof,the thermite steel enters the mold space through the pourmg cruci le andon to of the steel the slag fal1s,;

and, althou h thls islag is' 'of only approximatel hal the density ofthe steel already teeme in the. pouring gate and the mold space, itnevertheless, because of its momentum, strikes the top of the moltensteel in the gate 'with'sufficient force to-depress the metal and permitsome of the sla to enter the mold space, where, due to its 0 18.!-acteristic tendency to adhere to steel,- it

pieces to be welded, or, in the case of rail welding, is trapped underthe insert, and, although the steel surges back quickly, it

ate directly below the tap hole in the ,coats or forms a film over theends of the cannot force out the slag which has adhered to the surfacesor has been thus trapped," and the weld is irreparably'damaged;

I have discovered, however, that by diverting the slag containingportion of the molten charge from direct falling contact with the moltensteel in the gate-and directing this portion of the charge againstasurface of the mold ad acent to, the pouring gate and at an angletothe' axis of the pouring gate, the mognentuni of the charge will bedis sipated by the impact-against such surfaceand this portion of thecharge will flow indicates the mol cavity therein into which the ends ofthe this highly desirab uietly into the gate, so that no portion of 't eslag will reach the mold cavity or the the upper end of the latter, oneof the walls is diverted laterally to form a relatively flat angle withthe-longitudinal axis of the gate, fol-min an inclined surface 6 againstwhich the mo ter'fthermite charge T is directed, by positioning thecrucible C so that the bottom tap-hole thereof is vertically above suchsurface 6, whereby the force of the falling stream of slag and metalispractically dissipated and the molten mass flows quietly surface 6, asdescribed, is merely exem and may be changed or varied to sul theparticular conditions and, in fact,such impact surface. ma be located inthe top'surface of the mo (1 proper adjacent to and leading into thepouring gate; 7

What I claim 1s:

The method of forming slag free thermite welds in molds which comprisesteeming the slag, containing portion of said ch against a surface of themold adjacent t e entrance of the pouring gate, whereby the force'of thefallmg'charge in dissipated.

In testimony whereof I afiix my si ature.

JOHN H. DEPPE ER.

